Fish are helping researchers track down the origins of how brains compute mathematics, reports a review in Frontiers in Neuroanatomy. An international team has reviewed more than 200 publications, which together show that fish perceive quantities using parts of their brains similar to those used by mammals and birds. Research is still underway to find the specific brain circuitry that makes number processing possible, but these findings could eventually help treat human diseases that impair the ability to do math.